Goblins can make teleporter trinkets to Everlook (useless) and Area 52 (decently useful for getting to TK)
Gnomes can make teleporter trinkets to Toshley's Sttation (useless) and Gadgetzan (decently useful for getting to CoT / Hyjal)
Aside from that, you just really need to ask yourself a question: Do you like doing "cool" things, or do you like blowing shit up? Consider the difference between the Gnomish Poultryizer and the Goblin Rocket Launcher; this is the sort of subtle difference between gnomish and goblin engineers.
Ultimately though, it doesn't matter which you choose. You can still make all three epic goggles and the engineering gun as either spec.
_________________
Retcon, 70 BE Paladin, [H] Korgath-US (PVP)
"Just another plebe in an army of giants."